On Sat, 30 Apr 2016 08:54:45 -0700 (PDT), Harry K
wrote:

On Friday, April 29, 2016 at 9:17:50 PM UTC-7, wrote:
On Fri, 29 Apr 2016 22:22:54 -0400, wrote:

On Thu, 28 Apr 2016 11:06:10 -0400, wrote:

On Thu, 28 Apr 2016 06:38:04 -0400, wrote:

I wonder what would happen if someone took a small tire, such as the
ones on wheelbarrows or push carts (dollys) and just filled them with
Spray Foam (such as "Great Stuff" brand).

It would seem to me, that you could just remove the valve stem core,
insert the nozzle from the spray can into the valve stem, and fill the
tire. I guess the only concern would be to make sure the whole tire was
filled, and not leaving parts of it empty. The foam would expand and
make a solid tire.

Has anyone ever tried this?

My bet is the foam collapses and you still end up with a flat tire.
These tires carry 40-50 PSI of air, Put 40 pounds of force on a 1x1
stick against that foam and it will disappear into the foam.

If I could figure out how to inject it into the valve stem, I'd prefer
to fill them with concrete.

Just buy solid tires and be aware on soft ground, they suck. If you
are always running on a hard flat surface, they work great. Think rail
road wheels vs car tires

???Why would the suck on soft ground? On carts, hand trucks, garden trailers, etc. regular tires don't flex enough to be noticeable...actually I suspect they don't flex at all.

You suspect wrong.